c++中的一些类型转换 : CString,string,int ,long,double,char*,const char*,date等----留着备用

c++中的一些类型转换 : CString,string,int ,long,double,char*,const char*,date等

1. char* to string
string s(char *);  
注：在不是初始化的地方最好用assign().
！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！！
2. string to const char*
string a="strte";
const char* r=a.c_str();
注意是const的。还要转到char*：
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2.2. const char* to char*
const char* r="123";
char   *p1   =   new   char[strlen(r)+1]; 
strcpy(p1,r); 
附：http://hi.baidu.com/cfans/blog/item/06970ef4b671f366dcc4745d.html
 这个页面是具体讲述区别的。
·············································································································
3. cstring to string
vs2005 Unicode下：
  CStringW   str(L"test");   
  CStringA   stra(str.GetBuffer(0));   
  str.ReleaseBuffer();       
  std::string   strs   (stra.GetBuffer(0));   
  stra.ReleaseBuffer();

非Unicode下：
CString cs("test");
std::string str=cs.getBuffer(0);
cs.ReleaseBuffer();

注：GetBuffer()后一定要ReleaseBuffer(),否则就没有释放缓冲区所占的空间.
++++++++++++++++++++++++++++++++++++++++++++++++++++
4. double ,int to string
#include <sstream>
using namespace std;

stringstream ss; 
string result; 
long n=11111; 
stream << n; //从long型数据输入 
stream >>result; //转换为 string

===================================================

5.char*  to int, double ,long

char *s; double x; int i; long l;

s = " -2309.12E-15"; /* Test of atof */ 
x = atof( s ); 
printf( "atof test: ASCII string: %s/tfloat: %e/n", s, x );

s = "7.8912654773d210"; /* Test of atof */ 
x = atof( s ); 
printf( "atof test: ASCII string: %s/tfloat: %e/n", s, x );

s = " -9885 pigs"; /* Test of atoi */ 
i = atoi( s ); 
printf( "atoi test: ASCII string: %s/t/tinteger: %d/n", s, i );

s = "98854 dollars"; /* Test of atol */ 
l = atol( s ); 
printf( "atol test: ASCII string: %s/t/tlong: %ld/n", s, l ); 
------------------------------------------------------------------------------------------------
6. string to int ,long ,double             
              int s;
 string str="123";
 stringstream ss;
 ss<<str;//从str输入
 ss>>s;//输出到int
 ss.clear();

——————————————————————————————————————————
7. date to string
#include <time>
using namespace std;

char dateStr [9];
char timeStr [9];
 _strdate( dateStr);
printf( "The current date is %s /n", dateStr);
_strtime( timeStr );
printf( "The current time is %s /n", timeStr);

--------实践证明是正确的版本--------------------------------------------------------------
#include <iostream>
#include <ctime>
#include <cerrno>
 
int main()
{
     //Find the current time
     time_t curtime = time(0); 
      
      //convert it to tm
      tm now=*localtime(&curtime); 
     
     //BUFSIZ is standard macro that expands to a integer constant expression 
     //that is greater then or equal to 256. It is the size of the stream buffer 
     //used by setbuf()
     char dest[BUFSIZ]={0};
     
     //Format string determines the conversion specification's behaviour
     const char format[]="%A, %B %d %Y. The time is %X"; 
     
     //strftime - converts date and time to a string
     if (strftime(dest, sizeof(dest)-1, format, &now)>0)
       std::cout<<dest<<std::endl;
     else 
       std::cerr<<"strftime failed. Errno code: "<<errno<<std::endl;
}

|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
8.string to cstring

+++++++++++++++++++++++++++++++++++++++++++++++++++++
非Unicode下：
int 转 CString：
CString.Format("%d",int);
...............................
string 转 CString  
CString.format("%s", string.c_str());  
用c_str()确实比data()要好.  
.......................................
char* 转 CString  
CString.format("%s", char*);  
 CString strtest;  
 char * charpoint;  
 charpoint="give string a value";  
 strtest=charpoint; //直接付值
.....................................................
CString 转 int
 CString  ss="1212.12";  
 int temp=atoi(ss); //atoi _atoi64或atol
...................................................................................................................................
9.在Unicode下的CString to double 
CSting sTemp("123.567"); 
double dTemp = _wtof(sTemp.GetString());